1. Field of the Invention
This invention relates to an improved apparatus and method for converting binary coded decimal (BCD) numbers to binary numbers in a first mode of operation or for converting binary numbers to BCD numbers in a second mode of operation.
2. Description of the Prior Art
Many systems and apparatuses for converting between binary and binary coded decimal (BCD) numbers have been proposed and are well known in the art.
Some proposed systems can only convert BCD to binary, while other systems can only convert binary to BCD. Various approaches for converting from BCD to binary are described in the article "A Method for High Speed BCD-to-Binary Conversion", L.C. Beougher, Computer Design, March 1973, pp. 53-59. Similarly, approaches for converting from binary to BCD are described in the article "Binary-to-BCD Conversion with Complex IC Functions", John R. Linford, Computer Design, September 1970, pp. 53-61.
On the other hand, some proposed systems have the capability for converting both binary numbers to BCD and BCD numbers to binary. Examples of such dual operational capabilities are taught in U.S. Pat. Nos. 3,449,555 and 3,882,483.
U.S. Pat. No. 3,449,555 teaches the parallel conversion of signals representing multi-bit binary numbers to signals representing binary-coded decimal numbers and of signals representing binary-coded decimal numbers to binary numbers. A single modular logic net is used for each conversion.
In U.S. Pat. No. 3,882,483 read only memories include a programmed mapping between the binary and binary coded decimal codes. Input to the read only memory in one code is converted to an output in the other code. The outputs from the read only memories are then summed to produce the desired conversion.
However, in both of the above-referenced U.S. Patents, the same structure used for one type of conversion cannot be used for the other type of conversion. A different structural configuration, as well as signal flow, is required for each of the two types of conversion circuits in each of these referenced U.S. Patents.
Thus, none of the above-described systems teaches an apparatus which is capable of utilizing the same structure and signal flow to perform a conversion from BCD to binary in one mode of operation and from binary to BCD in another mode of operation.